Using Isotropic and Anisotropic Models to Determine Solar Module Tilt to Maximize Incident Energy and PV Electricity Output on the Alaska North Slope

The Alaska North Slope is a pristine and fragile arctic environment that needs protection. The present article illustrates the application of isotropic and anisotropic models for predicting solar radiation on photovoltaic (PV) modules (and, hence, potential electricity output) for different angles of inclination (or tilt) in Utqiagvik Alaska. The anisotropic model is shown to provide higher, albeit more accurate, predictions of solar radiation since it includes all of the measures used in the isotropic model, but provides a more comprehensive representation of the diffuse component. Specifically, the anisotropic model includes not only the isotropic part of diffuse radiation, but also the circumsolar and horizon brightening parts. A PV array angle of tilt of 55 degrees is shown to provide the greatest total amount of incident solar radiation for the entire year, based on both the isotropic and anisotropic models. However, both models also indicate that angles of tilt that are steeper than 55 degrees result in slightly greater amounts of incident solar radiation during the late-winter, early-spring, and mid-fall months; while angles of tilt that are flatter than 55 degrees result in slightly greater amounts of incident solar radiation during the summer and early-fall months. It is shown that a PV system with a moderately sized array, tilted at the fixed angle of 55 degrees, could provide more than 50 percent of the total annual electricity needs for homes in Utqiagvik Alaska.