Page 18 - North American Clean Energy March/April 2019 Issue

Bifacial PV
A new approach to PV rooftop design
by Alexandre G-Vanasse
Battery Energy Storage System
AC RACK L3060
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solar energy
THE LAST FEW YEARS BROUGHT SEVERAL NEW MODELS
of bifacial PV panels to the North-American PV market, along with a wide range of
prices and performances. Until recently, most bifacial PV panels were signi cantly more expensive than standard PV panels; project developers were often reluctant to o er such solutions, not knowing if the real eld performance would o set the extra cost. With price points for P-Type (lower bifacial e ciency) bifacial panels and polycrystalline bifacial panels closing in on standard mono PERC panels, and N-Type bifacial panels prices winding down (despite the tari ) the question developers should be asking is: “How do I make bifacial PV projects more pro table than standard projects?”
Rooftop is an ideal application for bifacial PV, due to the prominence of “cool” or “smart” roofs made of TPO and EPDM membrane, especially in states where they tend to be more popular, like California. ese can reach a re ectivity of 80 percent or more in the visible spectrum.
Designing for bifacial PVs is quite simple: the goal is to get as much light as possible to reach both the front and back sides of the panel. Initially, the designer looks at the type of structure, tilt angle, and height. Most racking solutions on the market are low pro le (at angles ranging between 3, 5, and 10 degrees), and feature a wind de ector, so it’s not necessarily easy to pick the right bifacial PV.
Imagine looking through a camera lens - the farther you move away from your subject, and the more tilt you give the camera, the wider your eld of view will be. is is similar to how a bifacial PV racking panel receives light on its backside: increasing tilt and height of the panel from the roof will boost its performance. is is demonstrated using PVSYSTS simulations, and in eld studies that are readily available online. e tricky part is choosing a racking solution; any rails under the panels will cause a line of
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MARCH•APRIL2019 /// www.nacleanenergy.com