There’s no one-size-fits-all approach when it comes to photovoltaic systems. Existing models can help users evaluate alternatives, and a new study looks at how effective such models are in northern climates.

Photovoltaic, or PV, systems use solar panels to generate electricity from the sun’s energy. Accurate predictions about panel effectiveness are critical for the design, financial analysis and monitoring of PV plants.

Good predictions require modeling of how much solar energy, or irradiance, will fall on the panels at any given time.

A team of University of Alaska Fairbanks and other researchers conducted a study to evaluate existing solar irradiance models for vertically mounted (i.e., straight up and down), bifacial PV systems, which have gained more attention in recent years.

Bifacial PV panels can generate electricity from both sides, allowing them to capture sunlight more efficiently than monofacial panels. And vertically mounted, east-west-facing bifacial arrays offer potential advantages by catching more morning and afternoon sunlight than traditional north-south-facing, fixed-tilt panels.

However, existing irradiance models for predicting vertically mounted, bifacial PV system performance had not been widely tested, especially in northern climates.

The researchers evaluated five models on bifacial PV systems in Golden, Colorado, (at 40°N latitude) and Fairbanks, Alaska, (65°N) for different types of solar arrays: east-west vertical, north-south vertical and south-tilted arrays.

None of the models made accurate predictions under cloudy or snowy conditions. And the models’ predictions were even less accurate at the higher-latitude location in Alaska.

Collecting high-quality data can improve the effectiveness of models at high latitudes, the researchers said. To obtain such data, the team recommends that potential PV system users monitor snow levels, measure solar irradiance using heated pyranometers (devices that measure solar irradiance on a flat surface) with sufficient power and service meteorological stations regularly.

“We’ve already seen that vertical east-west bifacial PV can be just as productive as traditional south-facing tilted PV at high latitudes. Plus, you get the benefit of more generation in the mornings and evenings,” said Henry Toal, a research engineer with the UAF Alaska Center for Energy and Power and an author of the study.

“If people are going to start installing systems like these in Alaska, it’s critical that we know what our existing models can and can’t do. This study is a huge step forward towards making sure that we’re prepared for the next generation of PV systems,” he said.

The other authors of the study include Erin Tonita and Karin Hinzer with SUNLAB at the University of Ottawa, Silvana Ovaitt and Chris Deline with National Renewable Energy Laboratory and Christopher Pike with Renewable IPP.

The study, “Vertical Bifacial Photovoltaic System Model Validation: Study with Field Data, Various Orientations, and Latitudes,” was published in the IEEE Journal of Photovoltaics.

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  Alaska, energy, north, pv